A steam cooker is a cookware which is used to cook foods via heat steam. The advantages of cooking with a steam cooker are no smoke, food that are not parched, resulting in foods that are healthier, more nutritious, and fresh. Generally, the steam cooker includes a main body, a pot mounted to the main body, a lid covered on the pot, and a backflow prevention device connecting the main body and the pot. The pot and the lid together form a cooking space for accommodating foods. In use, the main body heats water to form steam, which flows into the backflow prevention device and \into the pot to cook foods.
Generally, the backflow prevention device usually includes a seal member. In use, the steam pushes the seal member to move upwards to open the backflow prevention device, and then the steam flows into the pot from the main body. After use, the pot is moved out, and the seal member moves downward under its weight to seal the backflow prevention device. As such the main body and the pot are separated to prevent the liquid in the pot from diffusing outside when the pot is moved out.
However, the seal member depends on its weight to seal the backflow prevention device, which is unreliable, so that the liquid in the pot can diffuse out when the pot is drawn up.